Certificate of analysis raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2026-07-07 and is reviewed periodically as new material appears.
Laboratory work relies on standard behavioral paradigms. Rodents are tested in the elevated plus maze, open field, and passive avoidance tasks, with outcomes compared against diazepam or vehicle controls. Intranasal dosing is used most often because it bypasses first-pass metabolism, though intraperitoneal and intravenous routes also appear in published protocols. Biochemical endpoints include tissue BDNF concentrations, cytokine levels, and monoamine metabolites. Human data are limited to small Russian trials reporting reduced anxiety scores; most were not prospectively registered, and few employed independent outcome assessment.
Measuring peptide exposure inside the brain is technically difficult. Selank is degraded rapidly in plasma, and assays must separate intact peptide from fragments, which favors targeted mass spectrometry over immunoassays alone. Reported half-lives are short, on the order of minutes, so effects observed hours later are attributed to downstream signaling rather than to the parent compound. Blood-brain barrier permeability is debated and rarely quantified directly. Gaps include absent dose-response characterization, inconsistent reporting of purity, and almost no pharmacokinetic data from human participants.
Selank is studied chiefly as an animal-model anxiolytic with proposed secondary effects on memory and immune signaling. Reported mechanisms include modulation of the GABA-A receptor complex, inhibition of enkephalin-degrading enzymes, and shifts in monoamine turnover within limbic structures. Some experiments describe increased expression of brain-derived neurotrophic factor in the hippocampus after repeated dosing. No single molecular target has been confirmed, and the peptide does not bind any receptor with the selectivity typical of a conventional small-molecule drug. Mechanism therefore remains a set of hypotheses rather than an established pathway.
Outside its country of origin the compound is generally handled as a research chemical rather than an approved medicine. No regulatory approval from the United States Food and Drug Administration or the European Medicines Agency has been granted for human use. Identity and purity are normally checked by reverse-phase high-performance liquid chromatography, with mass spectrometry used to confirm the molecular mass. Lyophilised material is stored cold and desiccated, and repeated freeze-thaw cycles are avoided.
Published work on this peptide almost always uses intranasal delivery, with drops or a spray applied to the nasal mucosa. Some animal experiments have used subcutaneous or intraperitoneal injection, and a smaller number have compared routes directly. Oral administration is not a focus of the literature, because short peptides of this size are broken down by digestive enzymes and cross intestinal barriers poorly. How much of an intranasal dose reaches the bloodstream intact in humans remains an open question.
| Property | Value | Notes |
|---|---|---|
| Principal proposed target | GABA-A receptor complex | Hypothesis derived mainly from animal pharmacology |
| Common behavioral assay | Elevated plus maze | Rodent test for anxiety-like behavior |
| Reported molecular marker | Hippocampal BDNF expression | Measured by immunoassay or mRNA quantification |
| Typical dosing route | Intranasal | Chosen to reduce first-pass metabolism |
| Reported plasma half-life | Minutes | Based on limited peptide stability data |
Enzymatic stability motivates the extra three residues at the carboxyl end. Native tuftsin is cleaved quickly by circulating aminopeptidases and carboxypeptidases, which limits its duration of action and its usefulness as a tool compound. Extending the chain with proline-rich segments is a common design tactic because proline constrains the backbone and slows proteolysis. The same Pro-Gly-Pro motif appears in other Russian-developed peptides of the era. Whether the full seven-residue chain is required for activity, or whether it acts mainly as a prodrug releasing tuftsin, remains unresolved.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. Its four N-terminal residues reproduce tuftsin, a tetrapeptide fragment of the immunoglobulin heavy chain, while the C-terminal Pro-Gly-Pro extension is a synthetic addition. The peptide has a molecular mass near 752 daltons and carries a net positive charge at physiological pH because of the arginine and lysine side chains. Published indexes list it under the name Selank and the sequence abbreviation TKPRPGP. Solid-phase peptide synthesis is the standard production route for research quantities.
Regulatory status differs sharply by region. Selank holds a Russian marketing authorization, where it is supplied mainly as nasal drops, while authorities elsewhere have not approved it for medical use. Material sold internationally is therefore usually labeled as a research chemical rather than a medicine. Peer-reviewed publications come predominantly from Russian laboratories, and sample sizes are generally small. Whether the compound produces comparable effects under independent, well-controlled replication remains an open question that the broader literature has not settled.
Selank is a synthetic heptapeptide developed in Russia as a structural analogue of tuftsin, a naturally occurring immunomodulatory tetrapeptide. Its sequence, Thr-Lys-Pro-Arg-Pro-Gly-Pro, keeps the tuftsin core at the N-terminus and appends a Pro-Gly-Pro tail. Researchers at the Institute of Molecular Genetics in Moscow synthesized the compound during the 1990s while searching for peptides with combined anxiolytic and immunomodulatory activity. The added tail was intended to resist enzymatic cleavage and prolong the molecule's presence in circulation.
The compound has a calculated molecular weight near 751.9 daltons and carries a net positive charge at physiological pH because of its arginine residue. It dissolves freely in water and in common aqueous buffers, and typically appears as a white or off-white lyophilized powder. The amide backbone makes the molecule susceptible to peptidases, which limits oral use and favors intranasal or parenteral routes. Nomenclature in the literature varies: the substance is also described by the sequence abbreviation TP-7 and by a Russian trade designation.
Development work on the compound began in the 1980s and 1990s at the Institute of Molecular Genetics in Moscow, within the same research programme that produced the peptide Semax. Early investigators sought a tuftsin derivative with improved resistance to enzymatic breakdown and with activity in the central nervous system after peripheral administration. Most of the primary literature from this period was published in Russian, a factor that still shapes how easily the findings can be checked by outside groups.
Naming for this compound is not fully standardised in English sources. The spelling Selanc appears in some transliterations, and catalogue entries may instead list the peptide sequence itself as the identifier. Reference material sometimes groups it with other short synthetic peptides studied for behavioural effects, which can create confusion when citations are compared. Distinguishing the exact sequence from related tuftsin analogues is therefore a practical first step when reviewing any dataset or specification sheet.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, frequently abbreviated as TKPRPGP. It was designed as a structural analogue of tuftsin, a naturally occurring tetrapeptide released by enzymatic cleavage of the immunoglobulin heavy chain. The two additional proline residues at the C-terminal end extend the parent chain and change how the molecule behaves in solution. The free peptide has a calculated molecular mass of approximately 751.9 g/mol and is generally supplied as a lyophilised white to off-white powder.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography, with mass spectrometry used to confirm molecular mass and sequence information. Amino acid analysis and peptide mapping may supplement these methods. Certified reference standards are scarce, and many commercial lots are sold as research chemicals without a pharmacopoeial monograph. Regulatory treatment differs by country: Selank is a registered prescription medicine in Russia, while in the European Union and the United States it is not an approved drug and may fall under research-chemical or unapproved-product frameworks.
Selank is a hydrophilic peptide and dissolves readily in water and in aqueous buffers. The lyophilised powder is typically a white to off-white solid. Because short peptides are prone to hydrolysis and oxidation, handling benefits from limiting exposure to heat, moisture and strong light. Working solutions are commonly prepared in sterile water or saline, and repeated freeze-thaw cycles are avoided to reduce aggregation and loss of activity. These practices reflect general laboratory convention rather than published stability specifications.
==== Stable isotope labels ==== An approach for relative quantification that is more costly and time-consuming, though less sensitive to experimental bias than label-free quantification, entails labeling the samples with stable isotope labels that allow the mass spectrometer to distinguish between identical proteins in separate samples. One type of label, isotopic tags, consist of stable isotopes incorporated into protein crosslinkers that causes a known mass shift of the labeled protein or peptide in the mass spectrum. Differentially labeled samples are combined and analyzed together, and the differences in the peak intensities of the isotope pairs accurately reflect difference in the abundance of the corresponding proteins. Absolute proteomic quantification using isotopic peptides entails spiking known concentrations of synthetic, heavy isotopologues of target peptides into an experimental sample and then performing LC-MS/MS. As with relative quantification using isotopic labels, peptides of equal chemistry co-elute and are analyzed by MS simultaneously. Unlike relative quantification, though, the abundance of the target peptide in the experimental sample is compared to that of the heavy peptide and back-calculated to the initial concentration of the standard using a pre-determined standard curve to yield the absolute quantification of the target peptide.
Nadolol, sold under the brand name Corgard among others, is a medication used to treat high blood pressure, heart pain, atrial fibrillation, and some inherited arrhythmic syndromes. It has also been used to prevent migraine headaches and complications of cirrhosis. It is taken orally. Common side effects include dizziness, feeling tired, a slow heart rate, and Raynaud syndrome. Serious side effects may include heart failure and bronchospasm. Its use in pregnancy and breastfeeding is of unclear safety. It is a non-selective beta blocker and works by blocking β1-adrenergic receptors in the heart and β2-adrenergic receptors in blood vessels. Nadolol was patented in 1970 and came into medical use in 1978. It is available as a generic medication. In 2020, it was the 340th most commonly prescribed medication in the United States, with more than 700 thousand prescriptions.
=== Individual reactions === The removal of the blue checkmark and Twitter Blue have sparked controversy. Actress Alyssa Milano added to her Twitter profile that she would not be paying for Twitter Blue. The Twitter account for Elmo tweeted that, "Elmo will miss you, little blue check mark". The blue checkmark has also caused crosscurrents between Twitter users, with technology journalist Joanna Stern writing that she "likes editing tweets", and appears to have distanced herself from the blue checkmark. Morning Consult journalist Bobby Blanchard asked Twitter to remove his blue checkmark. Other personalities and entities appeared confused as to why their blue checkmarks appeared despite not subscribing to Twitter Blue, such as journalist Maggie Haberman, actors Ben Schwartz and Elijah Wood, astrophysicist Neil deGrasse Tyson, and the Massachusetts Institute of Technology. The Twitter account for the Auschwitz-Birkenau State Museum clarified that it had not paid for Twitter Blue either. Model Chrissy Teigen compared her blue checkmark to the film It Follows (2014) and was able to get hers removed by changing her username, telling speechwriter Jon Favreau. Favreau later stated that he believed Musk was "capricious" in his actions and did not want to be potentially suspended for unverifying his account. Likewise, stand-up comedian and actor Patton Oswalt changed his username to remove his blue checkmark. dril, part of Twitter's secretive list of users to promote and of "Weird Twitter", removed his blue checkmark by changing his display name to "slave to Woke".
==== Manifestations of systemic conditions ==== Occasionally systemic conditions may be the sole cause of gingival inflammation rather than merely influencing background plaque-induced gingivitis. Certain mucocutaneous produce gingival inflammation which may manifest as desquamative gingivitis or oral ulceration. Such conditions include lichen planus, pemphigoid, pemphigus vulgaris, erythema multiforme, and lupus erythematosus. Allergic reactions may also trigger gingival lesions. Sources of allergens include toothpastes, mouthwash, chewing gum, foods, additives, medicines, dental restorative materials, mercury, nickel and acrylic, acrylic. Plasma cell gingivitis is a rare condition thought to be a hypersensitivity reaction. Lichenoid lesions may also occur on the gingival mucosa.
It is a colourless paramagnetic gas that, being thermodynamically unstable, decomposes to nitrogen and oxygen gas at 1100–1200 °C. Its bonding is similar to that in nitrogen, but one extra electron is added to a π* antibonding orbital and thus the bond order has been reduced to approximately 2.5; hence dimerisation to O=N–N=O is unfavourable except below the boiling point (where the cis isomer is more stable) because it does not actually increase the total bond order and because the unpaired electron is delocalised across the NO molecule, granting it stability. There is also evidence for the asymmetric red dimer O=N–O=N when nitric oxide is condensed with polar molecules. It reacts with oxygen to give brown nitrogen dioxide and with halogens to give nitrosyl halides. It also reacts with transition metal compounds to give nitrosyl complexes, most of which are deeply coloured. Blue dinitrogen trioxide (N2O3) is only available as a solid because it rapidly dissociates above its melting point to give nitric oxide, nitrogen dioxide (NO2), and dinitrogen tetroxide (N2O4). The latter two compounds are somewhat difficult to study individually because of the equilibrium between them, although sometimes dinitrogen tetroxide can react by heterolytic fission to nitrosonium and nitrate in a medium with high dielectric constant. Nitrogen dioxide is an acrid, corrosive brown gas. Both compounds may be easily prepared by decomposing a dry metal nitrate. Both react with water to form nitric acid.
Sources: en.wikipedia.org
Construction was interrupted by Cuba's involvement in World War I, but it was completed on February 9, 1920. On opening day, hundreds of visitors from around Havana and the surrounding areas came to tour the facility, including the Provincial Governor of Havana, Colonel Alberto Barreras, who was also a Freemason. Governor Barrearas oversaw a twelve gun salute and a performance of La Bayamesa by the General Staff Band. Three flags were raised; the flag of Cuba, the flag of the Supreme Council of Cuba, and the flag of the Grand Lodge of Cuba. Priority was given to Freemasons, but anyone could apply for housing here. There were only four rules needed to become a resident here: Residents had to be someone who needed public charity to live, "...even if they got there through vices." Residents had to be homeless. If the resident wasn't a Freemason, they needed to have letters of recommendation. All residents needed to pay up to 100 dollars to secure housing. As the years went by, the name "Asilo," or Asylum, became increasingly problematic. The original business model of the Mercy Asylum under its previous owners from 1886 had been to take beggars off of the street and put them into the shelter. As Cuba's new sphere of academia and the social welfare science studies advanced, earlier common practices in charity and relief work were radically transformed. Around the world, people began associating the term asylum with places like Bellevue Hospital and Bethlem Royal Hospital, and the Freemasons wanted to avoid that association.
=== Argentina === In Argentina, the residency (Spanish, residencia) consists of a three to four years of practical and research activities in the field selected by both the candidate and already graduated medical practitioners. Specialized fields such as neurosurgery or cardio-thoracic surgery require longer training. Through these years, consisting of internships, social services, and occasional research, the resident is classified according to their residency year as an R1, R2, R3 or R4. After the last year, the "R3 or R4 Resident" obtains the specialty (especialidad) in the selected field of medicine.
=== Pharmacokinetics === Salvinorin A is effectively deactivated by the gastrointestinal system, so alternative routes of administration must be used for better absorption. It is absorbed by oral mucosa. It has a half-life of around 8 minutes in non-human primates.
Amino acid score is used to determine if a protein is complete. It is used along with the measure of protein digestibility that refers to how well a given protein is digested, to compare the proportion of essential amino acids found in one protein to the proportion in a "reference protein" considered to be complete.
==== Copyright of AI-generated content ==== A separate question is whether AI-generated works can qualify for copyright protection. The United States Copyright Office has ruled that works created by artificial intelligence without any human input cannot be copyrighted, because they lack human authorship. Some legal professionals have suggested that Naruto v. Slater (2018), in which the U.S. 9th Circuit Court of Appeals held that non-humans cannot be copyright holders of artistic works, could be a potential precedent in copyright litigation over works created by generative AI. However, the office has also begun taking public input to determine if these rules need to be refined for generative AI. In January 2025, the United States Copyright Office (USCO) released extensive guidance regarding the use of AI tools in the creative process, and established that "...generative AI systems also offer tools that similarly allow users to exert control. [These] can enable the user to control the selection and placement of individual creative elements. Whether such modifications rise to the minimum standard of originality required under Feist will depend on a case-by-case determination. In those cases where they do, the output should be copyrightable" Subsequently, the USCO registered the first visual artwork to be composed of entirely AI-generated materials, titled "A Single Piece of American Cheese".
Sources: en.wikipedia.org
Miners don't directly act as nodes, but do communicate with nodes. The mining process is primarily intended to prevent double-spending and get all nodes to agree on the content of the blockchain, but it also has desirable side-effects such as making it infeasible for adversaries to stifle valid transactions or alter the historical record of transactions, since doing so generally requires the adversary to have access to more mining power than the rest of the network combined. The mining process in bitcoin involves maintaining the blockchain through computer processing power. Miners group and broadcast new transactions into blocks, which are then verified by the network. Each block must contain a proof of work (PoW) to be accepted, involving finding a nonce number that, combined with the block content, produces a hash numerically smaller than the network's difficulty target. This PoW is simple to verify but hard to generate, requiring many attempts. PoW forms the basis of bitcoin's consensus mechanism. The difficulty of generating a block is deterministically adjusted based on the mining power on the network by changing the difficulty target, which is recalibrated every 2,016 blocks (approximately two weeks) to maintain an average time of ten minutes between new blocks. The process requires significant computational power and specialized hardware. Miners who successfully create a new block with a valid nonce can collect transaction fees from the included transactions and a fixed reward in bitcoins.
A notable feature of the murals in Kizil is the extensive use of blue pigments, including the precious ultramarine pigment derived from lapis lazuli from Afghanistan. In the classification of the art of the region by Ernst Waldschmidt, there are three distinct periods: the murals from the first phase are characterized by the use of reddish pigments, while those from the second phase used bluish pigments in abundance. The earlier paintings reflect more Greco-Indian or Gandharan influences, while the second ones show Iranian (Sassanian) influences. Later caves seem to have fewer legends and/or jatakas, being replaced by the repetitive designs of numerous small Buddhas (the so-called thousand Buddha motif), or sitting Buddhas with nimbuses. The paintings of the first two phases showed a lack of Chinese elements. The last phase, the Turkic-Chinese period, is most in evidence in the Turfan area, but in Kizil only two caves showed Tang Chinese influence. Another characteristic of the Kizil murals is the division into diamond-shaped blocks in the vault ceilings of the main room of many caves. Buddhist scenes are depicted inside these diamond-shapes in many layers on top of one another to show the narrative sequences of the scenes.
IUPAC definition "secular equilibrium", IUPAC definition (IUPAC Compendium of Chemical Terminology 2nd Edition, 1997) (in English) Radioactive Equilibrium, EPA definition Radioactive Equilibrium. An equilibrium as old as the Earth Archived 2019-07-28 at the Wayback Machine, radioactivity.eu.com, IN2P3, EDP Science
=== Biofuels, pharmaceuticals and biomaterials === The most popular biofuel is ethanol produced from corn or sugar cane, but this method of producing biofuels is troublesome and constrained due to the high agricultural cost and inadequate fuel characteristics of ethanol. A substitute and potential source of renewable energy is microbes that have had their metabolic pathways altered to be more efficient at converting biomass into biofuels. Only if their production costs could be made to match or even beat those of present fuel production can these techniques be expected to be successful. Related to this, there are several medicines whose pricey manufacturing procedures prevent them from having a larger therapeutic range. The creation of new materials and the microbiological manufacturing of biomaterials would both benefit substantially from novel artificial biology tools.
In 2008, she presented the Proms season on BBC Two; has also presented The Culture Show, BBC Young Musician of the Year and The Review Show; For Sky Arts, hosted programmes on Sky Arts 2; also presented Aida from Royal Albert Hall (March 2012) for The Rosenblatt Recitals; was named Music Broadcaster of the Year, winning the Silver Prize at the Sony Awards; has presented global opera broadcasts for Royal Opera, London, and hosted broadcasts of the Royal Shakespeare Company; in 2021, appointed Head of Arts and Classical Music TV. Matthew Kneale, writer (Jewish mother) Matthew Kramer (born 9 June 1959) author and editor of over twenty scholarly texts; philosopher and signatory of the Euston Manifesto; currently Professor of Legal and Political Philosophy at the University of Cambridge and a Fellow of Churchill College, Cambridge. He writes mainly in the areas of metaethics, normative ethics, legal philosophy, and political philosophy; Director of the Cambridge Forum for Legal and Political Philosophy; elected a Fellow of the British Academy, the United Kingdom's national academy for the humanities and social sciences. Arthur Koestler, novelist and critic Bernard Kops, poet Peter Kosminsky (born 21 April 1956) is a British writer, director, screenwriter and producer; has directed Hollywood movies such as White Oleander and television films like Warriors, The Government Inspector, The Promise, Wolf Hall and The State. Elena Lappin is a writer and editor.
Sources: en.wikipedia.org
Intranasal administration predominates in both animal and human research because it avoids hepatic first-pass metabolism. Injectable and intraperitoneal routes appear in animal work mainly for comparison.
Behavioral endpoints include time spent in open arms of the elevated plus maze and avoidance latencies. Biochemical endpoints include BDNF concentration, cytokine levels, and monoamine metabolite ratios in brain tissue.
Most published studies are small, originate from a limited number of laboratories, and lack independent replication. Dose-response relationships, measured brain exposure, and long-term outcomes are not well characterized.
Most published work uses intranasal application, either as drops or as a nasal spray. Injection routes appear in a smaller set of animal experiments. Oral use is uncommon in the literature because peptide breakdown and poor absorption limit this route.